This invention relates generally to centrifugal compressors and, more particularly, to a method and apparatus for reclaiming oil that accumulates in the bottom of a collector structure.
In centrifugal compressors of the type which are used in large chiller type air conditioning systems, there is an inherent tendency for oil to migrate from the transmission to other parts of the machine. It is therefore necessary in such systems to provide the capability of reclaiming this lost oil and returning it to the transmission so as to allow continuous operation of the machine and to avoid degradation of the heat exchanger performance brought on by oil contamination.
Typically, there is a need to extract oil from a stagnant area near the compressor inlet. An ejector is commonly used for this purpose, with the ejector being driven by high pressure discharge gas taken from the compressor discharge flange at the top portion of the volute. No attempt is made to reclaim the oil escaping into the aerodynamic portion of the compressor before it passes into the heat exchangers.
In a new centrifugal compressor design, the Applicant has found it attractive to use a collector in place of a volute in the area surrounding the impeller. In such a system, in addition to the problem of oil tending to collect near the inlet cavity as discussed hereinabove, there is also a problem with respect to the accumulation of oil in the collector. That is, whereas in the volute there are circumferential pressure gradients that cause gas to flow at velocities that are sufficient to propel the oil out of the volute, a collector exhibits circumferential pressure gradients to a much lesser extent and, as a result, oil tends to gather in the bottom of the collector. When this collection of oil becomes excessive, it will interfere with the proper flow of gas from the compressor.
It is therefore an object of the present invention to provide an improved oil reclaim system in a centrifugal compressor.
Another object of the present invention is the provision in a centrifugal compressor for reclaiming a portion of the oil that escapes into the aerodynamic portion of the compressor before it passes into the heat exchangers.
Yet another object of the present invention is the provision in a centrifugal compressor for the use of a collector structure rather than a volute.
Still another object of the present invention is the provision in a centrifugal compressor having a collector for avoiding the problem of oil buildup in the bottom of the collector.
Yet another object of the present invention is the provision in a centrifugal compressor for an oil reclaim system which is economical to manufacture and effective in use.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.